Michelle Boorstein, Washington Post Staff Writer, on the Trinity College Program on Public Values Survey:

The percentage of Americans who call themselves Christians has dropped dramatically over the past two decades, and those who do are increasingly identifying themselves without traditional denomination labels, according to a major study of U.S. religion being released today.

The survey of more than 54,000 people conducted between February and November of last year showed that the percentage of Americans identifying as Christians has dropped to 76 percent of the population, down from 86 percent in 1990. Those who do call themselves Christian are more frequently describing themselves as "nondenominational" "evangelical" or "born again," according to the American Religious Identification Survey.

The survey is conducted by researchers at Trinity College in Hartford, Conn., and funded by the Lilly Endowment and the Posen Foundation. Conducted in 1990, 2001 and last year, it is one of the nation’s largest major surveys of religion.

The increase in people labeling themselves in more generic Christian terms corresponds strongly with the decline in people identifying themselves as Protestant, the survey found. People calling themselves mainline Protestants, including Methodists and Lutherans, have dropped to 13 percent of the population, down from 19 percent in 1990. The number of people who describe themselves as generically "Protestant" went from approximately 17 million in 1990 to 5 million.

Meanwhile, the number of people who use nondenominational terms has gone from 194,000 in 1990 to more than 8 million.

"There is now this shift in the non-Catholic population — and maybe among American Christians in general — into a sort of generic, soft evangelicalism," said Mark Silk, who directs Trinity’s Program on Public Values and helped supervise the survey.

The survey substantiated several general trends already identified by sociologists: the slipping importance of denomination in America, the growing number of people who say they have "no" religion and the increase in religious minorities including Muslims, Mormons and such movements as Wicca and paganism.